Thermal Conductivity and Interfacial Thermal Resistance: Measurements of Thermally Oxidized SiO2 Films on a Silicon Wafer Using a Thermo-Reflectance Technique

Abstract

This article describes the development of a method to measure the normal-to-plane thermal conductivity of a very thin electrically insulating film on a substrate. In this method, a metal film, which is deposited on the thin insulating films, is Joule heated periodically, and the ac-temperature response at the center of the metal film surface is measured by a thermo-reflectance technique. The one-dimensional thermal conduction equation of the metal/film/substrate system was solved analytically, and a simple approximate equation was derived. The thermal conductivities of the thermally oxidized SiO2 films obtained in this study agreed with those of VAMAS TWA23 within ± 4%. In this study, an attempt was made to estimate the interfacial thermal resistance between the thermally oxidized SiO2 film and the silicon wafer. The difference between the apparent thermal resistances of the thermally oxidized SiO2 film with the gold film deposited by two different methods was examined. It was concluded that rf-sputtering produces a significant thermal resistance ((20 ± 4.5) × 10−9 m2·K·W−1) between the gold film and the thermally oxidized SiO2 film, but evaporation provides no significant interfacial thermal resistance (less than ± 4.5 × 10−9 m2·K·W−1). The apparent interfacial thermal resistances between the thermally oxidized SiO2 film and the silicon wafer were found to scatter significantly (± 9 × 10−9 m2·K·W−1) around a very small thermal resistance (less than ± 4.5 × 10−9 m2·K·W−1).